Skip to main content

Full text of "The Cambridge Natural History"

See other formats


genus to genus. The stomach is much saceulated. The dent
formula is I f C i-g-tt P f M f. The atlas is often open belo
forming thus an incomplete ring.
Though the number of the incisor teeth in the adu
Diprotodonts is never more than three on each side in each ja
more numerous rudiments are present. Mr. M. "Woodward 1 h
lately investigated the subject with interesting results. !
finds that many species present decided traces of two addition
incisors, raising the total to that which characterises the Pol;
protodontia; but in two cases, viz. Ma^TOp^ls giganteus and J?etr<
gale penicillata, a sixth is present, the total number being thi
in excess of that found in any other Marsupial. This, as tl
author himself admits, proves too much. No mammal is know
which in the adult condition has so many incisors; nor do th
fossil Mammalia help us to get over the difficulty; even amon
reptiles it is not usual for so many teeth to occur upon th
It is a curious fact that the two long lower incisors can b
used after the fashion of a pair of scissors, or rather a pair c
shears. Their inner edges are sharpened, and they are capabl
of some motion towards and away from each other; by thei
means grass is cropped.
The stomach of Macropits (and of other allied genera) i
peculiar by reason of its long and saeculated character; tin
oesophagus enters it very near the cardiac end, which is bifid
Messrs. Sehafer and "Williams 2 have shown that the squamoug
lion - glandular epithelium of the oesophagus extends over th<
greater part of the stomach, only the pyloric extremity and on<
of the two cardiac caeca being lined with columnar epithelium.
The Macropodidae are clearly divisible into three sub-families
which are distinguished by marked anatomical characters.
In the sub-family MACJROPODINAE (including the geners
Macropus, Petrogale, Lagorchestes, Dorcopsis, Dendrolagus, Onycho-
gale, and Lagostrophus) there is no hallux, and the tail is hairy
The oesophagus enters the stomach near the cardiac end. The
caecum when short has no longitudinal bands; the liver has a
Spigelian lobe.
The second sub-family, POTOROIINAE or HYPSIPKYMNINAE (in-
cluding the genera JPotorous, ^epyprymiMAS, jBettongict,, and Oalo-
1 JProc. Zool. Soc. 1893, p. 450.                                  2 IMd. 1876, p. 165.